Combined cycles meet the market need

Raw demand for large amounts of capacity will require quick addition of gas turbine combined-cycle plants

Tim Hennagir

Associate Editor

The installation of combined-cycle power plants has been an ideal and cost-effective way to meet national demands for electric power in global regions such as Southeast Asia and Latin America. And individual country markets, namely the UK, are currently experiencing a rush of orders for combined-cycle plants. Initial generating blocks are being made available in little more than a year, due to ever-decreasing installation and cycle times for prime mover installation.

Raising pressure ratios, increasing turbine inlet temperatures and improving component efficiencies has led to substantial increases in unit efficiency. Furthermore, the use of gas turbines in conjunction with a bottoming steam cycle now results in the highest efficiencies for fossil-fueled power plants because of higher gas turbine efficiencies. Three-fourths of all gas turbines are currently used in combined-cycle plants. The technology is being implemented in just under 35 percent of the total worldwide fossil-fueled power plant capacity under construction. Additional combined-cycle capacity additions in the same percentage range are forecast for the next 10 years.

In a competitive market situation, customers continue to demand faster payback on their power plant investment and want vendors to deliver products faster and cheaper without compromising quality. At the forefront of manufacturers` recent improvements for combined-cycle plants is the all-important drive toward higher efficiency. The push to reach the plateau of larger turbine sizes is testing equipment vendors` ability to balance efficiency without a subsequent decline in availability or reliability features valued by customers.

Equipment manufacturers are pinpointing and exerting even more pressure to win orders in international markets for their higher efficiency combustion turbine prime movers. During the past few years, advanced technology developments have brought efficiency levels for gas turbines to the 60 percent threshold. Manufacturers ABB Power Generation, GE Power Systems, GEC Alsthom/European Gas Turbines, Westinghouse Power Generation, Rolls-Royce Plc., Pratt & Whitney and Siemens Power Generation/KWU remain optimistic about current and future global markets for gas-fired, combustion turbine plants.

The world power market is shifting to advanced combined-cycle technology because of the favorable economics that result from its high efficiency and low emissions. With global power market deregulation and privatization driving new competition, power producers are moving away from an initial cost-per kilowatt focus to a life-cycle, bottom-line emphasis on cost-per-kilowatt hour.

Asia`s power appetite

Because of dramatic need, power generation is experiencing a dynamic revolution in the entire Asian Pacific region. Generating capacity is expected to grow annually at an average of 5.3 percent until the end of the decade, with a modest slowdown to 4.6 percent by the year 2010. There is a move toward independent power producers and there is an overwhelming expansion in power infrastructure development.

With Indonesia`s annual electricity demand increasing an average of 15 percent for the last 10 years, state-owned utility PT Perusahaan Listrik Negara (PLN) began a series of plant orders to increase capacity as quickly as possible. One of these contracts is the 135 MW Sengkang, South Sulawesi project, which continues to progress towards completion. This contract represents ABB Power Generation`s first IPP project in Indonesia. The order with ABB was placed by PT Energi Sengkang, a joint venture between PT Triharsa Sarana Jaya Purnama of the Republic of Indonesia, and two Australian companies, Energy Equity Corp. Ltd. and Tenneco Holdings Pty Ltd. The first of the two GT8C gas turbines at Sengkang was synchronized this July; full combined-cycle operation is anticipated by August 1998.

Today`s gas turbines achieve availability in the 95 percent range. This level is more than competitive with standard steam power plants that typically run several percentage points lower, said Dominic A. Bartol, general manager with Westinghouse Electric Corp.`s Power Generation Technology Division, during his keynote address at ASME Turbo-Expo `97 in Orlando, Fla. “The first 150 MW to 180 MW F engine went into operation at the turn of the decade. Today, there are approximately 145 F-class engines in operation from all industrial vendors, with net combined-cycle thermal efficiencies starting to exceed 57 percent.”

Capacity for Korea

Four major Westinghouse-supplied combined-cycle power projects in Korea are testament to the company`s fleet performance: Ilsan; 600 MW (4×1 501D5) combined-cycle; Puchon, 450 MW (3×1 501D5) combined-cycle; Ilsan Extension, 300 MW (501D5) and Korea Electric Power Co. (KEPCO), Ulsan, (4×2 501F). According to Westinghouse, the 501D5 and 501 F turbines` power ratings are ideal fits for the required block sizes and capacities needed in many countries of the world, in particular 150 MW, 300 MW and 500 MW to 600 MW.

The 501D5 and the more advanced 501 F offer high thermal efficiencies and availability consistent with fully verified and proven design techniques for advanced gas turbines. Westinghouse`s power projects in South Korea have helped further dramatic electric sector expansion plans, primarily through the establishment of the so-called “new cities” to relieve growth in Seoul. Additionally, gas-fired combined-cycle plants offer the flexibility for not only meeting electric power demands, but also the capability of supplying district heating for these developing cities.

According to Joergen Haslestad, head of power plant projects and marketing for Siemens Power Generation/KWU in Asia, his company has booked power plant orders totaling more than 7,000 MW from the Far East. Siemens recently announced it would supply GUD combined-cycle technology for its first private power plant in South Korea. LG Energy Co., Seoul, a subsidiary of South Korean LG Group (formerly Lucky Goldstar), awarded Siemens a contract for the Bugok combined-cycle plant that includes two gas turbines, one steam turbine, the associated generators and an entire instrumentation and control system.

Siemens will supervise the construction and commissioning of the 500 MW Bugok plant, which will be located about 120 km southwest of the capital city of Seoul. In May 2000, the plant`s first gas turbine generators will go on line; combined-cycle duty is scheduled to commence at the beginning of 2001 when the steam turbine-generator is connected. The plant is being designed with an efficiency of 58.8 percent and will be operated primarily on natural gas, with oil as alternate fuel.

In addition to providing eight GT24 combustion turbines, ABB Power Generation will build a 2,000 MW power plant near Poryong for Korea Electric Power Co. (KEPCO). The station will be one of the largest and most efficient combined-cycle plants in South Korea and will supply electricity to the utility`s rapidly growing base of industrial and residential customers. Construction of the plant began in April 1996. When fully operational, this plant is expected to achieve overall fuel efficiency in excess of 59 percent, ABB reports.

“The key to experience is not just the number of units, configurations and operating hours [a vendor provides], but also operating situations in diverse conditions around the world, ” said Robert L. Nardelli, president and chief executive officer, GE Power Systems. For example, at KEPCO`s Seoinchon plant, where starting and stopping the units is required six days a week, eight GE F technology gas turbines have recorded more than 10,800 starts in five years of service.

According to GE, the Seoinchon facility was recently expanded to 4,000 MW, making it the world`s largest combined-cycle plant in operation and also the most efficient, with a combined-cycle net thermal efficiency of 55 percent for Blocks 1 and 2 and 57 percent for Blocks 3 and 4. Other large power projects in Asia featuring GE`s F technology include Tokyo Electric Power Co.`s 2,800 MW Yokohama plant, China Light and Power`s 2,500 MW Black Point station and the Electricity Generating Authority of Thailand`s 2,130 MW Ratchaburi plant. GE is supplying six MS9001FA gas turbines and three steam turbines (in total, three STAG 209FA systems) for Ratachaburi, which is scheduled to enter service by the year 2000. This plant is expected to be one of the largest gas turbine projects awarded this year.

U.K. market madness

The combined-cycle gas turbine (CCGT) project market in the UK is changing once again. Initially, trailblazing projects such as Enron`s Teeside or Scottish Hydro`s Keadby sold baseload power under firm, 15-year sales and purchase agreements. There are now projects to serve a variety of market segments. Some plants are designed for mid-merit generation (InterGen`s 750 MW Rocksavage), while other stations are dispatched for peaking and other ancillary services to the National Grid (Destec`s 160 MW Indian Queens). IVO`s Humber II plant sells tolling capacity to gas suppliers.

According to Oxford Economic Research Associates (Oxera), the future UK market holds additional promise for even more CCGT capacity. A recent report issued by the independent economic advisory service confirms the UK is riding the wave of its “second dash for gas.” Oxera estimates that in the next seven years, all of the new generating capacity that is added in the country (between 14 GW and 23 GW) will be gas-fired in nature. Conversely, seven years ago, gas-fired plants held only 1 percent market share.

PowerGen Plc`s development of a wholesale gas trading business enabled the company to respond quickly to changes in UK electricity and gas prices by selling gas directly into the market, or using it to fuel the combined cycle power plants. The decision to diversify into gas led to plans for three such stations: Killingholme, 900 MW on Humberside; 740 MW Rye House in Hertfordshire and Connah`s Quay at 1,400 MW. The latter plant is fired entirely by `sour` gas from the nearby Liverpool Bay gas field, in which PowerGen holds a stake. The station is also equipped with a surplus natural gas treatment plant, which feeds into the National Gas Transmission System. Built by GEC Alsthom, Connah`s Quay has a thermal efficiency of 55 percent, ranking it among the most technically advanced such stations worldwide.

A major factor in the choice of turnkey contractor for Connah`s Quay was the development of GEC Alsthom`s 9FA gas turbine. Originally introduced at 212 MW, the 9FA machine has been uprated to 255.6 MW for simple-cycle and 390.8 MW for combined-cycle operation. These turbines are manufactured by GEC Alsthom subsidiary European Gas Turbines (EGT) at its Belfort works near Paris. EGT was also awarded a three-year maintenance contract for its four 9FA machines at Connah`s Quay.

In mid-October, GEC announced it had won yet another order for a gas-fired power plant in the UK. AES Partington Ltd., a subsidiary of Virginia-based US independent power developer AES Corp., awarded GEC an order for a 380 MW, gas-fired combined-cycle station to be built on the site of an earlier plant at Partington near Manchester. The project is scheduled to enter commercial operation in time to meet demand for power during the winter season of 1999 and 2000. GEC Alsthom will supply the plant under a turnkey contract; GEC`s Power Plant Group, based at Knutsford in the UK, will carry out construction and project management. Partington will also incorporate the 9FA gas turbine, which together with the steam turbines, generators and boiler plant will be supplied from GEC Alsthom factories in the UK and France. AES Corp. owns or has interest in five major UK power plants; GEC has supplied more than 4,500 MW of large gas-fired generating capacity installed or under construction in the UK.

According to ABB Power Generation, the company`s high combined-cycle efficiency GT26 promises to be an excellent performer when used in baseload operation. Sequential combustion has also set new industry standards for load following and cycling duty. At Rocksavage in the UK, two, 240 MW GT26 generators will be supplied by ABB for InterGen and ICI`s 750 MW combined-cycle project at Runcorn. ABB will also provide the associated heat recovery steam generators, one steam turbine generator and auxiliary equipment. GT26 single-shaft combined cycle plants are also designed for fast start at 58.5 percent efficiency for 50 Hz markets. Rocksavage is expected to be fully commerical early next year.

“Most of our target plant and combined-cycle concepts will remain single shaft,” says Randolf Listmann, ABB Power Generation Ltd. combined-cycle product manager in Baden, Switzerland. “In past years, this type of arrangement has been proven as the right choice by more and more of our customers. This layout gives the highest operational flexibility and availability.”

The recently announced 1,500 MW CCGT station at Staythorpe will also use the GT26 as its prime mover. National Power Plc. is developing the project in partnership with ABB. Construction is expected to begin early in 1998 on the site of two former coal-fired plants northeast of Nottingham. When fully operational in 2003, the plant will produce enough electricity for up to two million people.

ABB will supply gas turbines, boilers, steam turbines, the associated heat recovery steam generators and the overall plant control system, balance of plant equipment and civil work. ABB is also responsible for engineering and complete installation and commissioning. Staythorpe will be the sixth gas-fired power plant delivered by ABB in the UK since the country`s electricity supply sector was privatized in 1990.

For Siemens Power Generation/KWU, King`s Lynn is the company`s fourth combined-cycle power plant order received from an English customer. Incorporation of a V94.3 high-temperature gas turbine, triple-pressure reheat process as well as a hydrogen-cooled generator has increased projected plant efficiency by about 4 percentage points, as compared to a concept using the previous Siemens V94.2 product line.

“King`s Lynn is our first single-shaft order for our advanced technology turbine, the V94.3. This plant will help Eastern Electricity in a deregulated UK market that is becomeing more efficiency and performance driven. The order is a landmark in terms of opening the UK market, changing regulations and creating a new niche for more efficient plants,” said Dr. Robert Taud, Siemens Power Generation/KWU director of marketing for steam/combined-cycle technology/fossil-fired power plants. The 347 MW station is in final stages of commissioning and was scheduled for provisional turnover this fall. King`s Lynn is expected to operate at 55 percent efficiency.

Latin America landmarks

“In Latin America, privatization and legal changes are creating near-term opportunities for combined-cycle power plants. In order to meet the rapidly growing demand for electricity, private capital will be required. Regional market growth will be driven by increasing population, improving economies and political stability,” said ABB`s Listmann. A consortium consisting of ABB and Babcock Wilcox Espanola will supply a 775 MW combined-cycle power plant to Central Dock Sud S.A., an independent power producer operating in Argentina`s deregulated market. ABB recently announced this latest GT26 order. Construction began the middle of this year, with the first units scheduled to provide power within 24 months. The plant is scheduled for completion in the third quarter of 1999.

For Siemens Power Generation/KWU, 1996 was a banner year in the region. It secured orders for six of its advanced .3A gas turbines in South America. In partnership with several noted international engineering and energy development companies, Siemens has begun supplying gas turbine units to five key power plant projects in Argentina, Chile and Peru. According to Siemens Power Generation/KWU and its US-based operation Siemens Power Corp., robust economic growth and continued privatization efforts by South American governments have helped fuel the increasing demand for Siemens power generation technology in the region.

Last August, a consortium comprising Siemens Power Generation/KWU and Black & Veatch received an order to repower Unit 13 of the Luyan de Cuyo steam power plant outside of Mendoza, Argentina. The project calls for upgrading the existing 125 MW steam turbine and boosting the overall plant output to more than 500 MW by installing a Siemens Model V94.3A gas turbine in a GUD (combined-cycle) arrangement. The order, placed by CMS Generation Co, also includes a six-year service contract.

A consortium including Siemens, Black & Veatch and SADE Ingeneria y Construcciones S.A. was awarded a turnkey contract early last year for the construction of the 660 MW GUD power plant in Genelba, Marcoz Paz, a Buenos Aires province. The contract calls for Siemens to supply two .3A gas turbines, a steam turbine, instrumentation and controls, as well as electrical distribution equipment. Purchasing the plant is Compania Naviera Perez Companc S.A., a private stock company headquartered in Buenos Aires. The full combined-cycle is expected to produce power at 55 percent efficiency and will be operational sometime in early 1998. Total cost of this Siemens contract was US$490 million.

Colombia represents one of the more challenging Latin America markets for scope of supply, delivery schedule and construction of combined-cycle power projects. The challenges of working in a country with limited infrastructure creates special challenges with transportation, communication and access to required labor skills. Westinghouse Electric Corp.`s ability to overcome these obstacles was one of the reasons the company was selected by Banco Ganadero of Panama, Consortio Columbiano Industrial (CCI) and Illinova Generating Co. for a turnkey power plant and long-term maintenance agreement. The contract calls for supply for a 150 MW combined-cycle plant for Los Flores 1, located in Barranquilla, Colombia. Two units totaling 250 MW began operating at the Los Flores site in 1995. The third 150 MW unit was recently commissioned. Los Flores was expanded on a merchant basis.

Westinghouse received another Colombian order from EPC contractor Bechtel Corp. to supply equipment for the 240 MW ThermoEmcali power projects in Cali. Westinghouse will supply a 160 MW 501 F combustion turbine and 85 MW steam turbine-generator as well as supply parts, repair, project management and technical installation services. The baseload facility, which will burn natural gas or No. 2 oil, is expected to be at commercial operation in May 1998. The project owners are InterGen of Boston, Maas, and Emcali and Corporacion Financeria del Pacifico of Colombia.

An InterGen-led consortium closed financing in mid-April for the 234 MW gas-fired TermoEmcali power project. The BOT project is sponsored by a partnership of International Generating Co. of Boston, Empresas Municipales de Cali and Corporacion Financiera del Pacifico, for a total cost of $210 million. TermoEmcali sets a number of international precedents, according to developer InterGen, including being the first 144A-financed power project bond in the country without a Colombian state-owned company as offtaker and the longest project bond issued in Colombia to date. Construction of the project began at the end of March, with completion expected by February 1999. Distral is building the heat recovery steam generator for TermoEmcali.

Industrial power innovation

The steel industry is one of the largest consumers of electric power. Many steel companies, especially those in Europe, are showing a renewed interest in improving their traditional power plants by taking advantage of low calorific gases produced by ironworks and using them as gas turbine fuels in combined-cycle power plants. Thanks to the progress achieved by a number of gas turbine manufacturers in combustion of low Btu gases, byproducts of the steel industry are gaining favor as fuel for gas turbine-based power stations.

The 505 MW Tarente combined-cycle power plant in southern Italy (CET 3) was designed and constructed under a turnkey contract by a joint venture of Ansaldo Industria and Turbotechnica, Nuovo Pignone`s engineering company for gas turbine-driven power plants. This is the first application where centrifugal compressors have been used in a single-shaft arrangement with a GE MS90001/E gas turbine.

A mixture of three steel industry off-gases (coke oven, basic converter and blast furance) feeds Tarante, with a low heat value of between 6,174 and 8,372 kJ/Nm3. The plant is probably the largest combined-cycle in the world in commercial operation fed by low Btu gas. First operational results have confirmed a net plant efficiency of about 45 percent. Iniziative Sviluppo Energie (ISE) owns the thermal power plants at Tarente. ISE was subjected to one of the first privatization actions in Italy, and ISE is now controlled by a company belonging to Edison SpA, Italy`s largest independent power producer, and Electricite de France.

Tarente has three combined cycles, each generating 168 MW. Ground was broken at CET 3 in January 1995 and the plant began commercial operations in less than two years. On Nov. 7, 1996, the first gas turbine generator began operation and the second and third units began generating on Nov. 21 and Dec. 23, 1996, respectively. Today, the plant is in industrial commissioning, which is scheduled to conclude by year`s end. Although CET 3 has only been connected to the grid for a short time, it has already generated 2.5 billion kWh. Eventually, Tarente is expected to generate 3,900 GWh of electricity per year and will make it possible to nearly double ISE`s generating capacity from 600 MW to 1,100 MW.

Blast furnace fuels

As already indicated, CET 3 uses gas recovered from the steelmaking manufacturing cycle as its main fuel. The gas from the blast furnaces is taken to the power plant in pipes 3.6 meters in diameter. The coke oven gas is taken to the power plant by pipes 2.6 meters in diameter the steel mill gas is taken to the plant by pipes 1.2 meters in diameter. The three gases, which differ from one another in their physical/chemical characteristics and their caloric value, are processed, mixed and then compressed before they are sent to the intake of the gas turbine power feed units. The pressure of the gases from the steel mill is slightly higher than the atmospheric pressure. The gases are filtered using electrostatic filters to eliminate particulates.

The coke oven gas and the steel mill gas contain more impurities, so that they undergo preliminary filtering. The blast furnace gas is mixed in with the other two gases and the mixture is filtered again. The mixture of the three steelmaking gases at the output of final filtering is sent to each module through a centrifugal compressor that has several stages, including an intermediate cooling stage and liquid separator. In the compressor, the mixture is raised to a pressure of 20 bars, which is required for the thermal cycle in the gas turbines. Before the turbine, the caloric value of the steelmaking gas mixture is measured and enriched by a sufficient amount of natural gas. A hot torch designed for each module allows the gas mixture to escape during the operating transients, since the gas may not yet be ready for turbine burning.

With this particular industrial power plant application, it is more economical to generate electricity by a combined cycle than by a conventional steam cycle. Iron industry byproduct gas treatment and compression costs do, however, create higher investment needs than a natural gas combined cycle of the same output. Nevertheless, this consideration, plus energy saving and emissions control aspects, has fostered various government incentives in many countries to construct similarly fueled combined cycles.

Power prospectus

The continued, growing demand for higher thermal efficiencies and power plant availability makes many global markets promising targets for combined-cycle power generation. This trend is likely well into the early years of the next decade, as deregulation and privatization of electricity sectors continues throughout the world.

Raw demand for large amounts of capacity will require quick addition of gas turbine combined-cycle plants. However, clients are not willing to pay for technology alone. Vendors must be able to reduce total lifecycle time and $/kW cost to maintain market share. While current markets for global equipment are expected to continue at a modest pace over the next several years, the long-term future looks even livelier.

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Taiwan Power Co. will expand its Tung Hsiao plant southwest of Taipei with the addition of a sixth, 320 MW combined-cycle unit. Previously, ABB Power Generation supplied Units 3, 4 and 5 at the plant; Units 4 and 5 are pictured here. ABB will provide two GT11N2 gas turbines to expand the plant`s capacity to 1,700 MW.

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Siemens Power Generation (KWU). A consortium including Siemens Power Generation, Black & Veatch and SADE Ingeneria y Construcciones S.A. was awarded a turnkey contract early last year for the construction of the 660 MW GUD power plant in Genelba, Marcoz Paz, Argentina. The full combined-cycle is expected to produce power at 55 percent efficiency and will be operational sometime in early 1998.

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Westinghouse Electric Corp. is supplying a 150 MW 501D5 gas turbine for the Los Flores 1 project in Colombia. Consortio Columbiano Industrial (CCI) and Illinova Generating Co. awarded Westinghouse the turnkey power plant contract and long-term maintenance agreement.

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The 505 MW Tarente combined-cycle power plant in southern Italy (CET 3) was designed and constructed under a turnkey contract by a joint venture of Ansaldo Industria and Turbotechnica, Nuovo Pignone`s engineering company for gas turbine-driven power plants. (Photo courtesy of Marc Morceau, La Phototheque, Electricite de France)